I have a Kindle Touch, a Kobo Touch and now a Kobo Mini. Like you, I couldn't resist getting it at the sale price. I love it! It's really really cute for starters. I think I squeed like a little girl when I saw how tiny it was. The screen is very readable. Some people have said that the Mini screen looks worse than the Touch screen but I haven't noticed a difference. Because of the device's size, you have to turn the page more but I don't mind. I really like that I can hold the reader in just one hand even though my hands are small. It's very comfortable for me to read on.
Overall, I would say that it's a very pleasant second (or third - gulp!) reader. It's the one I take with me to read when I have to wait someplace. Not only is the size right for travel, but if something happens to it (hopefully never), I'm only out $50.